1. Technical Field of the Invention
The present invention relates to a mounting structure for mounting a semiconductor chip on a wiring substrate such as a mother board, particularly to a semiconductor device in which thermal stress between the semiconductor chip and the mother board is absorbed to improve mounting reliability, and a manufacturing method thereof.
2. Description of the Related Art
A known flip chip connection structure includes a solder bump on a semiconductor chip that directly contacts a wiring land on a mother board, where the semiconductor chip is formed of silicon and is mounted on a wiring substrate, such as the mother board, that is primarily formed of resin, such as epoxy. The flip chip structure has a simple structure and is capable of easy mounting. However, because silicon and resin, whose coefficients of thermal expansion are different from each other, are directly connected, thermal stress occurs between the semiconductor chip and the mother board due to the difference of their coefficients of thermal expansion. The thermal stress is applied to the solder bump or the wiring land and causes a crack in the solder bump that breaks the connection of the semiconductor chip and breaks wire connections to the chip. To absorb such thermal stress, there has conventionally been proposed a structure in which underfill resin having a coefficient of thermal expansion, whose value is between those of silicon and resin, is filled between the semiconductor chip and the motherboard. However, using such an underfill resin causes a problem because the semiconductor chip cannot be removed for replacement.
For this reason, art to absorb thermal stress occurred between the semiconductor chip and the mother board without using the underfill resin is described, and Japanese Patent No. 2738711 proposes a structure as the wiring land of the mother board, where an electrode structure has free deformation characteristic and spring characteristic in horizontal directions, thermal stress is absorbed in such a manner that the thermal stress deforms the wiring land, and crack in the solder bump is prevented. A manufacturing method to realize the structure is that a lift off film is formed on the surface of the mother board, a metal film where the wiring land is formed is formed on the lift off film, and a pattern is formed on the metal film so as to have a bent shape or a curve shape in horizontal directions. Further, the wiring land, where a pattern is formed, has a structure that one end portion thereof is fixed to the motherboard, and the lift off film is etched and removed thereafter, so that the wiring land is formed as an electrode where the other end portion is in a floating state above the motherboard surface. Accordingly, since the wiring land to be formed, that is, the electrode is a cantilever electrode, whose one end portion is fixed and the other end portion is a free end in the floating state, thermal stress occurred is absorbed by deformation due to free deformation characteristic and spring characteristic of the electrode by bonding the solder bump of the semiconductor chip with the other end portion, and thus crack of the solder bump is prevented. The similar art is described in Japanese Patent Laid-open No. S63-177434, No. S64-50539, and No. H1-303731.
However, this art requires a process of forming the lift off film and removing it by etching in order to form the electrode in the floating state on the mother board surface, which makes a manufacturing process complicated. Further, since the other end portion of the electrode floats above the mother board surface, there is a danger that the electrode formed on the mother board surface may be deformed or broken when it touches other parts, foreign material, or the like. Furthermore, in the state where the semiconductor chip is bonded with the electrode of the floating structure by the solder bump, the semiconductor chip is in an unstable state for the motherboard due to elasticity of the electrode, and there is also a danger that the semiconductor chip easily drops from the motherboard by external force.
Moreover, although the wiring land of the mother board is formed as the electrode of the floating structure in the conventional art, the number of the wiring land is very large because of a large size of the mother board, which makes it difficult to preferably manufacturing all wiring lands, and thus there exists a problem that manufacturing yield is poor and the mother board becomes expensive as a result. Consequently, a structure is possible that the conventional wiring land structure is used for the mother board as it is, the semiconductor chip is mounted on a middle substrate referred to as an interposer, and the chip is mounted on the mother board via the interposer. For example, it is a structure as described in Japanese Patent Laid-open No. 2000-164635 in which the semiconductor chip is mounted on the interposer substrate and an electrode such as a solder ball is used as an external electrode. The interposer substrate is formed using a material having the same coefficient of thermal expansion as that of the mother board, an electrode structure is formed between the semiconductor chip and the interposer to absorb thermal stress, and thus eliminating thermal stress between the mother board and the interposer. With this art, since the structure to absorb thermal stress may be adopted only for the interposer, the manufacturing yield improves and the motherboard can be prevented from becoming expensive.
The art described in Japanese Patent Laid-open No. H1-155633,for example, is possible as the electrode structure to absorb thermal stress in the interposer substrate. In this art, an organic film with conductor is inserted between the semiconductor chip and the mother board, one end portion of the conductor provided for the organic film is connected with the solder ball of the semiconductor chip, and the other end portion of the conductor is connected with the wiring land of the mother board. Then, the conductor is formed in the cantilever structure so as to create spring characteristic, and it is possible to absorb thermal stress between the semiconductor chip and the wiring board.
However, in the art described in the gazette, because the structure of the conductor provided for the organic film with conductor is substantially same as the structure of the electrode of the floating structure, which has been applied for the mother board described in the foregoing gazette, it requires the manufacturing method by the lift off film and the manufacturing process becomes complicated. In addition, it is easily broken because the conductor has the floating structure, and the semiconductor chip is in the unstable state when it is mounted on the interposer due to elasticity of the conductor, and there is a danger that the semiconductor chip easily drops by external force.
An object of the present invention is to provide a semiconductor device that can be easily manufactured and can stably hold the semiconductor chip while thermal stress occurred between the semiconductor chip and the substrate mounting the chip is absorbed, and a manufacturing method thereof.
A semiconductor device according to the present invention comprises: a first member having a first electrode; and a second member having an insulating substrate and a second electrode formed on the surface of the insulating substrate and connected with the first electrode. The second electrode is constituted as a connection electrode that is easily peeled off from the surface of the insulating substrate in a connection region with the first electrode than the other region.
As a first mode of the semiconductor device of the present invention, it is the semiconductor device that comprises: a semiconductor chip having a conductor bump; and a mounting substrate having an insulating substrate and a connection electrode formed on the surface of the insulating substrate and with which the conductor bump is connected. The connection electrode has a structure that it is easily peeled off from the surface of the insulating substrate in the region where the conductor bump is connected than the other region.
As a second mode of the semiconductor device of the present invention, it is the semiconductor device that comprises: a semiconductor chip having a conductor bump; an interposer mounting said semiconductor chip; and a mother board mounting said interposer. Said interposer has: an insulating substrate; a connection electrode formed on the surface of said insulating substrate, one end portion being connected with the conductor bump of said semiconductor chip, and the other end portion being integrally supported by said insulating substrate; and a conductor ball formed on a rear surface of said insulating substrate and connected with the other end portion of said connection electrode. Said mother board has a wiring land connected with the conductor ball of said interposer. Said interposer is formed of a material having the same or substantially equal coefficient of thermal expansion as that of said mother board, and said connection electrode has a structure that the one end portion where said conductor bump is connected is easily peeled off from the surface of said insulating substrate than the other end portion.
As a third mode of the semiconductor device of the present invention, it is the semiconductor device that comprises: a semiconductor chip having a conductor bump; an interposer mounting said semiconductor chip; and a mother board mounting said interposer. Said interposer has: an insulating substrate; a connection electrode formed on a rear surface of said insulating board; and a conductor ball provided at one end portion of said connection electrode, said conductor ball being connected with a wiring land of said mother board. Said conductor bump of said semiconductor chip mounted on a surface of said insulating substrate is connected to the other end portion of said connection electrode. Said interposer is formed of a material having the same or substantially equal coefficient of thermal expansion as that of said semiconductor chip, and the connection electrode has a structure that the one end portion of the connection electrode is easily peeled off from a bottom surface of said insulating substrate than the other end portion.
Herein, it is preferable that the surface of the insulating substrate on which the connection electrode is formed is formed in a rough surface and a constitution is made such that connection electrode is formed in a close contact state with convex portions of the rough surface. Furthermore, the connection electrode is one that an interconnecting portion connecting one end portion with the other end portion is formed in a bent pattern shape on the surface of the insulating substrate, and the one end portion and the interconnecting portion are formed so as to be easily peeled off from the surface of the insulating substrate.
Further, in the manufacturing method of the semiconductor device of the first mode that comprises: the first member having the first electrode; and the second member having the second electrode formed on the surface of the insulating substrate and connected with the first electrode, the manufacturing method of the second member includes the steps of: forming a through hole on a required position of the insulating substrate; performing processing to reduce a degree of surface activeness of the surface of a region other than the region of the through hole on the surface of the insulating substrate; and forming the second electrode formed of the connection electrode with a required pattern in the region including the through hole on the surface of the insulating substrate, in which the second electrode is connected with the insulating substrate in the through hole region, and formed in the state that it is easily peeled off from the surface of the insulating substrate in the region other than the through hole.
In the manufacturing method of the present invention, the step of performing processing to reduce the degree of surface activeness of the surface other than the region of the through hole on the surface of the insulating substrate further includes the steps of: making the region on the surface of the insulating substrate become a rough surface to form fine concave portions and convex portions; and coating surface low active agent on the surface of the insulating substrate to leave the agent in the concave portions, and the step of forming the second electrode further includes the steps of: plating a conductive material on the surface of the insulating substrate and the inner surface of the through hole to form a plated film; and forming the plated film in a required pattern to form a through hole electrode and the connection electrode respectively on the through hole inner surface and the surface of the insulating substrate, in which the second electrode is in the state that it connects with the through hole electrode in one portion and closely contacts with the insulating substrate at the vertex of the convex portions of the insulating substrate in another portion.
Alternatively, in the manufacturing method of the present invention, the first member is the semiconductor chip, the first electrode is the conductor bump provided for the semiconductor chip, and the second member is the interposer for mounting the semiconductor chip on the mother board, which has substantially equal coefficient of thermal expansion to that of the mother board, in which the through hole electrode penetrating the insulating substrate of the interposer in a thickness direction is formed, the second electrode, which is formed of the connection electrode connected with the through hole electrode at the other end portion, is formed on the surface of the insulating substrate, and the conductor ball, which is connected with the through hole electrode to make connection with the mother board, is formed on the rear surface of the insulating substrate.
Moreover, in the manufacturing method of the present invention, the first member is the interposer mounting the semiconductor chip, which has coefficient of thermal expansion substantially equal to that of the semiconductor chip, the first electrode is the conductor ball provided for the interposer, the second member is the mother board, and the second electrode is the wiring land provided on the surface of the mother board, in which the through hole electrode penetrating the insulating substrate of the interposer in a thickness direction is formed, and the connection electrode is formed, in which the through hole electrode is connected with the other end portion on the rear surface of the insulating substrate and the conductor ball is disposed in one end portion.
According to the semiconductor device of the present invention, when thermal stress occurs between the first member and the second member based on the difference of coefficient of thermal expansion and the thermal stress is applied to the first electrode and the second electrode, the connection electrode is peeled off from the surface of the insulating substrate of the second member in one portion to absorb thermal stress by elastic deformation of the connection electrode, and thus breakage of the first electrode and the second electrode is prevented. Further, since the connection electrode is in a close contact state with the second member when thermal stress is not applied, the first member can be mounted in a stable state.